FPGA CLE with two independent carry chains

Abstract

The invention provides an FPGA comprising an array of identical tiles. Each tile comprises a logic block that includes a Configurable Logic Element (CLE). In one embodiment, the CLE is implemented in two similar portions called "slices". Each slice has a separate carry chain. In a CLE with four function generators, each carry chain incorporates the outputs of two function generators.

What is claimed is: 
     
       1. A Configurable Logic Element (CLE) comprising: first, second, third, and fourth function generators each having inputs and at least one output;   a first carry chain incorporating said outputs of said first and second function generators, said first carry chain having a carry-in terminal and a carry-out terminal;   a second carry chain incorporating said outputs of said third and fourth function generators, said second carry chain having a carry-in terminal and a carry-out terminal; and   an input multiplexer having a plurality of inputs; wherein: the carry-in and carry-out terminals of the first carry chain are independent from the carry-in and carry-out terminals of the second carry chain, and   at least one such input multiplexer input can drive through said input multiplexer both at least one said input of at least one of said first and second function generators and at least one said input of at least one of said third and fourth function generators.     
     
     
       2. The CLE of claim 1, wherein: at least one such input multiplexer input can drive through said input multiplexer at least one input of each of said first, second, third, and fourth function generators.   
     
     
       3. A Configurable Logic Element (CLE) comprising: a plurality of function generators each having inputs and at least one output;   a plurality of carry chains each having a carry-in terminal and a carry-out terminal, each such carry chain incorporating said outputs of at least one such function generator; and   an input multiplexer having a plurality of inputs; wherein: the carry-in and carry-out terminals of each such carry chain are independent from the carry-in and carry-out terminals of each other such carry chain in the CLE, and   at least one such input multiplexer input can drive through said input multiplexer at least one said input of at least one such function generator incorporated in each such carry chain.     
     
     
       4. The CLE of claim 3, wherein: said plurality of function generators comprises at least four function generators;   said plurality of carry chains comprises at least two carry chains; and   said outputs of at least two such function generators are incorporated in each of said at least two carry chains.   
     
     
       5. A Configurable Logic Element (CLE) comprising: first, second, third, and fourth function generators each having inputs and at least one output;   a first carry chain incorporating said outputs of said first and second function generators, said first carry chain having a carry-in terminal and a carry-out terminal;   a second carry chain incorporating said outputs of said third and fourth function generators, said second carry chain having a carry-in terminal and a carry-out terminal; and   an output multiplexer having a plurality of outputs; wherein: the carry-in and carry-out terminals of the first carry chain are independent from the carry-in and carry-out terminals of the second carry chain, and   at least one such output multiplexer output can be driven through said output multiplexer by both at least one said output of said first and second function generators and at least one said output of said third and fourth function generators.     
     
     
       6. The CLE of claim 5, wherein: at least one such output multiplexer output can be driven through said output multiplexer by said output of each of said first, second, third, and fourth function generators.   
     
     
       7. A Configurable Logic Element (CLE) comprising: a plurality of function generators each having inputs and at least one output;   a plurality of carry chains each having a carry-in terminal and a carry-out terminal, each such carry chain incorporating said outputs of at least one such function generator; and   an output multiplexer having a plurality of outputs; wherein: the carry-in and carry-out terminals of each such carry chain are independent from the carry-in and carry-out terminals of each other such carry chain in the CLE, and   at least one such output multiplexer output can be driven through said output multiplexer by at least one said output of at least one such function generator incorporated in each such carry chain.     
     
     
       8. The CLE of claim 7, wherein: said plurality of function generators comprises at least four function generators;   said plurality of carry chains comprises at least two carry chains; and   said outputs of at least two such function generators are incorporated in each of said at least two carry chains.